1. Field of the Invention
The present invention relates generally to a fuel injection rate limiting device for a diesel engine.
More particularly, it relates to an improved design for such a limiting device, wherein the maximum engine torque for the normal load range is set by means of a limiter which prevents the control element of a governor to shift excessively in the fuel increasing sense and, should the engine speed (rpm.) begin to fall due to overloading, the governor's control element is allowed to shift gradually in the fuel increasing sense against a torque spring to raise the engine torque to avoid stopping of the engine to thus impart a reasonable degree of tenacity to engine operation.
2. Description of the Prior Art
As a like device of prior art is known, among others, one shown in FIG. 1, wherein a governor lever 51 is urged, on the one hand, by a governor spring 53 in the direction indicated by the arrow "r" with a fulcrum shaft 52 as the fulcrum for the fuel injection rate of a fuel injection pump 54 to be increased accordingly and, on the other hand, by a governor force 55 in the direction "l" for said fuel injection rate to be decreased accordingly and the position of the governor lever 51 is determined by the difference between said two opposing urging forces to either increase or decrease the fuel injection rate.
When the engine in operation has been overloaded, the governor force 55 decreases as the engine speed (rpm.) falls and the governor lever 51 is shifted in the fuel increasing direction "r".
Then, first a limitee 56 formed on the governor lever 51 is checked by a limiter 57 and further increase of the fuel injection rate is thereby prevented. If, nevertheless, the governor lever 51 should continue shifting in the same direction, the limitee 56 thereon then starts pushing the limiter 57 to thereby compress a torque spring 58 urging it back gradually for the fuel injection rate to be increased accordingly so that the engine is kept in operation.
If the overload should further continue increasing, with no proper action taken for eliminating its cause, a checker 59 monoblock with the limiter 57 is stopped by a torque adjusting screw 60, the limitee 56 is prevented from further shifting in the direction "r" and, with the fuel injection rate no longer increased, the engine is caused to stall under overload.
Numeral 61 is a crank case or a gear case, 62 a fixed cylinder, 63 a lock nut, 64 a cap nut and indicated by numeral 65 is the stroke (extent) of increase of fuel injection rate under overload.
In the construction shown in FIG. 1 the stroke of fuel increase feasible on cold starting is limited to that of fuel increase under overload 65 and, this being insufficient, the engine's starting performance cannot be satisfactory.
In such a case, required additionally is a special start-assisting arrangement such as a priming device for additionally supplying, separately, an auxiliary fuel for assisting starting to thereby improve the engine's starting performance, and this is unadvantageous in that the engine as a whole becomes more complicated in construction, more bulky and expensive and also the starting procedure is complicated thereby.
For overcoming the abovementioned problems, now known is the construction shown in FIG. 2.
The construction of FIG. 2 represents the following improvements made in the construction shown in FIG. 1. In it there are additionally provided a spring holder 66 and a spring for allowing fuel increase on starting (fuel increase-on-starting spring) 67 between said torque spring 58 and said adjusting screw 60, and a stopper 68 in formed monoblock with the spring holder 66. The fuel increase-on-starting spring 67 is stronger in tension than the torque spring 58, and remains uncompressed even when the torque spring 58 is compressed with the engine running under overload. The spring holder 66 urged as shown by the fuel increase-on-starting spring 67 is checked by the stepped part 69.
On starting of the engine, the governor force 55 is zero, hence the limitee 56 shifts in the fuel-increase direction "r" with an increased force. Hence the torque spring 58 as well as the fuel increase-on-starting spring 67 is compressed for the fuel supply to be increased for starting with its rate corresponding to the sum of the fuel increase stroke under overload 65 and the fuel increase stroke on starting 70, and the engine's starting performance is improved thereby.
This construction of FIG. 2, however, has a drawback that the tension of the torque spring 58 is not adjustable, hence it is impossible to adjust to a proper level the peak torque when the engine speed (rpm.) falls under overload.
In order to further overcome this drawback, the inventor developed the construction shown in FIG. 3 prior to the present invention.
It is so designed that the torque spring 58 alone is compressed when the running engine is overloaded. On starting of the engine, the torque spring 58 is compressed and at the same time also compressed is the fuel increase-on-starting spring 67 with a movable cylinder 71 sliding in the fuel-increasing direction "r" for the fuel injection rate to be increased for starting. The tension of the torque spring 58 is adjustable by means of an adjusting screw 72 and that of the fuel increase-on-starting spring 67 by means of another adjusting screw 73 respectively.
This construction of FIG. 3, however, still has such a drawback as the extent of shifting of the movable cylinder 71 in the fuel-increasing direction "r" on starting of the engine, that is, the fuel-increase stroke on starting 70 is unstable being liable to be too large or too small, this possibly resulting in a failure to sufficiently improve the starting performance due to shortage of fuel or in an imperfect combustion with consequent emission of black smoke and/or waste of fuel due to excessive fuel supply.